Composite Laminates Compression After Impact Testing

A compression after impact (CAI) test is used to define the damage resistance of composites after an impact event. An impact on a composite laminate panel may result in no visible external damage, but it may generate a dramatic reduction of compressive strength. The design of automotive parts using composite materials should consider the effects of impact on the material properties. This data can be obtained by following dedicated standards (i.e. ASTM D7136M, ASTM D7136) using an Instron Drop Tower configured with CAI accessories.

THE CHALLENGE

While having excellent mechanical properties (i.e. strength and stiffness) with a lower weight, compared to their metallic counterparts, composites can exhibit poor tolerance to damage caused by impact. The types of damage can be complex, irregular in shape, and may affect all layers of the structure. Additionally, they may be barely visible or hidden from view.

Low-energy impacts can be considered the most dangerous since the damage they cause may go unnoticed during routine visual inspections of the impacted surface. Impact energies that cause visible damage to the component may be significantly higher than those that have a significant effect on the mechanical properties.

The study of damage tolerance of laminates and the effect of different impact energies on residual strength is crucial.

Our Solution

With the Instron® 9350 impact droptower, the damage tolerance of laminates can be studied, and the effect of different impact energies on the residual strength can be determined. Performing a CAI test on components shows that materials respond differently to different impact conditions, and enable engineers to design and test composite products more cost effectively.

When configured with an instrumented tup, data acquisition, and software, the force signal from each impact can be captured and analyzed, helping engineers improve their knowledge about the material’s performance. The addition of a special temperature chamber allows the user to investigate how the same material may react in high-temperature environments up to 300°C.